Caption: Luis W. Alvarez (1911-1988), American physicist. He joined Ernest Lawrence's Radiation Laboratory at Berkeley in 1937, and worked on radar and the atomic bomb during World War II. In the 1950s he played a major role in developing the bubble chamber and his team at Berkeley discovered numerous new particles with it. Alvarez won the physics Nobel prize for this work in 1968. In the 1970s and 1980s Alvarez became involved in other areas, including the discovery of an iridium layer in Cretaceous/Tertiary boundary clay and the theory that a comet crashed to Earth at the end of the Cretaceous era & caused the death of the dinosaurs. He is seen in his room at the Lawrence Berkeley Laboratory in 1984.